The establishment of the species-delimits and varietal-identities of the cultivated germplasm of Cucumis melo and Cucumis sativus in Sri Lanka using morphometric, organoleptic and phylogenetic approaches

Cucumis melo L. (vern. Kekiri) is an important but underutilized vegetable in Sri Lanka, traditionally used for both culinary and medicinal purposes. Despite its cultural significance, the genetic and phenotypic diversity of Sri Lankan C. melo germplasm has remained largely unexplored. In contrast, C. melo and C. sativus cultivars in developed countries have been extensively characterized, with rich genomic resources available to support crop improvement. This study aimed to establish species delimitation and varietal identities of cultivated C. melo and C. sativus germplasm in Sri Lanka using morphometric, organoleptic, and molecular approaches. An island-wide germplasm collection was undertaken, including 11 C. melo and 9 C. sativus genotypes, which were assessed using IPGRI descriptors, field morphological trials, and consumer preference analyses. Organoleptic evaluation revealed complex sensory profiles across cooking, salad, and fruit varieties, with sweetness emerging as a key determinant of preference in fruit types, while bitterness negatively influenced salad varieties. Molecular barcoding using rbcL and trnH-psbA markers enabled phylogenetic analysis, species delimitation, and divergence dating. Results indicated clear genetic differentiation between C. melo and C. sativus germplasm, with divergence estimated at ~ 23 million years, older than previous reports. Concatenated marker analysis improved resolution of varietal relationships, supporting conservation and breeding applications. This integrative study provides the first comprehensive characterization of Sri Lankan C. melo germplasm, establishing a foundation for its promotion as a vegetable, medicinal resource, and valuable genetic pool for future crop improvement.